20-27 kg / 45-60 lb. You may also find some of the tennis strings you purchase offer a recommended tension range. For example, Babolat’s RPM Blast recommends 48 – 66 lbs or 22 – 30 kg, a rough guide for understanding where they have determined the string performs its best.
At a minimum, every tennis player should understand the basic trade-offs among comfort, power, control, and spin in relation to string tension. Any decent tennis racquet will have a recommended range of string tensions, for example, 58 to 68 pounds. When we talk about low or high tension, it makes sense to confine ourselves within no more than 10% outside this range, because at extremely low tensions, some of the normal correlations break down.
As soon as a racquet is strung, it will lose tension before it goes anywhere near a tennis ball. It's said that strings can lose up to 10% within 24 hours. So if you string at 55 lbs but don't plan to use your racquet for a week, then it will have lost quite a bit of tension by the time you finally play.
Your skill level on court is the final question that needs to be addressed in order to nail down your ideal string tensions. Here are those tension ranges again, narrowed down even further for each playing level. Nylon/Gut: 50-60lbs (22.5-27kg) Power: 50-55lbs (22.5-25kg) Beginner: 54-55lbs (24.5-25kg)
First, remember that tension is really a matter of personal preference. Even the pros' tensions are all over the map -- some string as low as the mid-to-high 30-lbs range, while others are as high as 70+ lbs, with most others sprinkled somewhere in the middle.
In general, thinner string will provide more power and spin, while thicker strings provide more control and durability. Tension Each racquet will have a specific tension range that the manufacturer recommends you string within, usually around 50-60 pounds.
I’ve been playing with polyester strings (Luxilon Alu Power, Luxilon Alu Power Rough, Volkl Cyclone) strung between 50-55lbs in the Babolat Pure Aero line of racquets for the past 10 years but notice that I rarely break the strings (often play 30+ hours without breaking the strings).
The study compared two identical tennis racquets, one strung at 40 pounds and one strung at 70 pounds (the same tensions as in our previously mentioned spin study). The impact apparatus can be set up to simulate a player hitting a topspin groundstroke, and we can measure the ball rebound spin using a high speed video camera operating at 240 frames/sec.